There was a thread a few weeks (months?) back about build-it-yourself
amphibious VW's.  The link below is about an Australian guy who took a WWII
US amphibious jeep (alot larger vehicle than the schwimmingwagon),
converted it into a seagoing Winnebago, and actually circumnavigated the
globe in it.  The guy died in 1981 but the vehicle is still on display at
his old grammer school in Perth.

 http://www.iinet.net.au/~daveb/halfsafe/halfsafe.html